1. The Field of the Invention
This application relates generally to drilling devices and methods. In particular, this application relates to latches for wireline drill assemblies for use in sonic drilling processes.
2. Background and Relevant Art
Often, drilling processes are used to retrieve a sample of a desired material from below the surface of the earth. In sonic drilling process, an open-faced core drill bit is attached to the bottom or leading edge of a core barrel. The core barrel is attached to a drill string, which is a series of threaded and coupled drill rods that have been connected together. The core barrel is vibrated and optionally rotated and pushed into the desired sub-surface formation to obtain a sample of the desired material (often called a core sample). Often, the core barrel is positioned within an outer casing. In some cases, the outer casing and the core barrel may be advanced simultaneously. The outer casing can be used to maintain an open borehole and can be utilized to install wells, instruments and for many other purposes.
In drilling processes using wireline systems, the core barrel and the casing are advanced together into the formation. The casing has a drill bit connected to a drill string and is advanced into the formation. However, the core barrel does not necessarily contain a drill bit and is removable from the drill string in a core barrel assembly, allowing the drill string to remain in the hole. The core barrel assembly includes at least the core barrel and a head for attaching to a wireline. In normal operations, the core barrel assembly is lowered into the drill string until the head reaches a portion of the casing that engages with a latch on the head to restrict the movement of the core barrel assembly with respect to the casing. Once latched, the core barrel assembly advances into the formation along with the casing, causing material to fill the core barrel. When the core sample is obtained, the core barrel assembly is retrieved separately from the casing using a wireline system, and the core sample is removed. The wireline system removes the time needed to trip the drill rods in and out of the borehole to obtain a core sample.
Wireline systems are not usually used in sonic drilling processes because vibrations created during sonic drilling can be very destructive to components of a core barrel assembly, particularly latches. Conventional latches are easily damaged and destroyed in a sonic drilling process, leading to inefficiencies in repairing broken equipment and in partial samples. Additionally, traditional latches in wireline core barrel assemblies are not designed to resist both upward and downward forces on the core barrel assembly. The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein can be practiced.